Oh, Ding... the sex hasn't disappeared, it's just off taking a nap. Falling asleep next to your lover means that you get to wake up next to him, too. And if he was tired enough to pass out as soon as his head hit the pillow, how good could the sex really have been if he'd tried to force it?

Next time, let him sleep. Then in the morning when you're both refreshed (and sober) you can make it clear that he's not going anywhere until he's made love to you.

Was it a lot of beer? Once, way back when I was visiting the spouse during college, we both passed out/fell asleep during lazy cuddly foreplay. It happens. That's when you wake up and romp! Also, you can tease him about it and get extra.